1. Field of the Invention
The present invention is in the field of firearms and pertains particularly to methods and apparatus for enabling a trigger mechanism to switch firing modes from semi-automatic to full automatic under variable applied pressure to the trigger component of the mechanism, the pressure resulting in a change in position of the trigger.
2. Discussion of the State of the Art
In the field of firearms there are rifles manufactured for military use. A good example of such a rifle is an M-16 rifle. The M-16 rifle is a military weapon that typically has three firing modes governed by a safety selector, the three modes including a safety mode, a semi-automatic mode, and a fully automatic mode. The safety selector mechanism built into the wall of the lower receiver unit and integral to the trigger system is set manually by an operator of the weapon.
In safety mode the rifle will not fire. In semi-automatic mode a hammer is released and strikes a firing pin when a user pulls the trigger. Expanding gas from the barrel drives a retraction bolt backward against a spring, resulting in ejection of the spent shell casing and loading of a new shell. The retraction bolt causes the hammer to rotate back into trigger position where it is automatically latched by the disconnector until the trigger returns to full forward, so a second shot cannot be fired while the trigger is still being pulled. When the trigger returns forward the disconnector is released and the hammer rests on the forward end of the trigger. A notch provided in the hammer seats against the trigger and the disconnector moves back and is no longer latching the hammer. The trigger mechanism is then ready to release the hammer to fire a next shot. It has occurred to the inventor that switching from semi-automatic to fully automatic mode for an M-16 and like rifles need not be solely a manual process. Therefore, what is clearly needed is a pressure activated trigger mechanism that enables mode selection between semi-auto and full auto through the application of pressure on the trigger, changing position of the trigger.